In the related art, an intake device provided with a seal surface which is made up of an inner wall surface with which a valve body comes into contact is known (refer to, for example, JP 2010-1847A (Reference 1)).
Reference 1 described above discloses a variable intake device which is provided with an intake control valve capable of opening and closing an opening portion provided in a collector and is switchable between a first port in which intake air passes through the opening portion in a case where the intake control valve is at an opening position, and a second port in which intake air detours without passing through the opening portion in a case where the intake control valve is at a closing position. A seal lip made of a rubber material is provided at an outer peripheral end portion of the intake control valve of the variable intake device. Further, in the variable intake device, a configuration is made such that in a case where the intake control valve is at the closing position, the seal lip and an inner wall surface of the opening portion come into contact with each other, whereby the opening portion is closed by the intake control valve, and an overhang portion, provided so as to overhang toward the inside of the opening portion from the inner wall surface of the opening portion, and the seal lip come into contact with each other, thereby suppressing the occurrence of a striking sound due to the contact of a portion in which the seal lip is not formed, of the intake control valve with the inner wall surface of the opening portion. Here, the overhang portion is formed over the entirety of four sides of the inner wall surface of the opening portion.
However, in the intake control valve of Reference 1 described above, since the overhang portion provided so as to overhang toward the inside of the opening portion from the inner wall surface of the opening portion is formed over the entirety of four sides of the inner wall surface of the opening portion, an opening area of the opening portion is reduced by an amount corresponding to the overhanging of the overhang portion over the entirety of the four sides. For this reason, an intake air flow path in the first port in which intake air passes through the opening portion narrows, and as a result, there is a problem in that pressure loss of intake air in a case where the intake control valve is at the opening position increases. Further, in a case where an overhang amount of the overhang portion is reduced in order to suppress an increase in pressure loss of intake air, the seal lip and the overhang portion become prone to come into contact with each other at a position deviated from a proper contact position. For this reason, a case where the intake control valve is deviated with respect to the opening portion, whereby the opening portion is not sufficiently closed, or a case where the intake control valve over rotates without contact at a proper contact position, or the like is considered to easily occur. As a result, there is a problem in that it is not possible to sufficiently maintain sealing properties (close contact properties) between the intake control valve and the opening portion.